Fluid treatment device and method

ABSTRACT

An apparatus and method for treating raw water. The apparatus comprises a vessel having an inlet for the raw water and an outlet for the skimmed water, and wherein the vessel contains the raw water, and a rotor mechanism for creating a plurality of gas bubbles within the raw water. The apparatus further comprises a disperser device, operatively associated with the rotor mechanism, for dispersing the plurality of gas bubbles from the rotor mechanism within the vessel, and wherein the gas bubbles create an oily froth on the top of the raw water, and a skim tray, positioned about the rotor mechanism, is provided for removing the oily froth from the top of the raw water as well as a secondary skimmer positioned within the skim tray. In one preferred embodiment, an external skim tank that is configured to deliver a gas to the rotor mechanism and wherein the external skim tank is configured to receive the oily froth from the secondary skimmer.

BACKGROUND OF THE INVENTION

This invention relates to a fluid treatment device and method. Moreparticularly, but not by way of limitation, this invention relates to anapparatus and method to recover hydrocarbons from fluid streams.

In the course of producing and refining hydrocarbons, operators producefluid streams that contain impurities. As those of ordinary skill in theart will recognize, produced streams contain hydrocarbons that requireseparation. Many times, an operator may wish to discharge the producedstream into a body of water, or inject the produced water intopredetermined subterranean zones. Government regulations address thecontent of the discharge fluid streams. Also, operators do not wish tobe the cause of pollution. Therefore, various types of prior artseparation devices have been developed. However, prior art devicessuffer from several deficiencies. For instance, in order to adequatelyseparate the water from the hydrocarbons, large pieces of equipment arerequired. A large foot print (area occupied by the separation equipment)is needed. However, many times hydrocarbons are produced and/or refinedin remote areas where space is a premium.

Hence, there is a need for a device and method that will effectively andefficiently separate hydrocarbons and other impurities from an effluent.There is also a need for a device and method that can be used withvarious types of fluid streams. Also, there is a need for a device thatcan be used in conjunction with other type of prior art separationdevices. There is also a need for a device and method that creates asmall foot print. These and many other needs will be met by thefollowing disclosure.

SUMMARY OF THE INVENTION

An apparatus for treating a raw water is disclosed. The apparatuscomprises a vessel having an inlet for the raw water and an outlet forthe skimmed water, and wherein the vessel contains the raw water, and arotor mechanism for creating a plurality of gas bubbles within the rawwater. The apparatus further comprises a disperser means, operativelyassociated with the rotor mechanism, for dispersing the plurality of gasbubbles from the rotor mechanism within the vessel, and wherein the gasbubbles create an oily froth on the top of the raw water, and a skimmingmeans, positioned about the rotor mechanism, for removing the oily frothfrom the top of the raw water.

In one preferred embodiment, the apparatus further comprises an externalskim tank that is configured to deliver a gas to the rotor mechanism andwherein the external skim tank is configured to receive the oily frothand gas from the skimming means.

The apparatus may also contain a pump and centrifuge for separating ahydrocarbon component and a water component from the oily froth withinthe external skim tank, and wherein the water component from thecentrifugal pump is directed to the vessel. A heat exchange method mayalso be included that is operatively associated with either the externalskim tank or the primary process vessel so that heat is added to theoily froth or the process stream.

The disperser means, in one preferred embodiment, comprises a dispersermechanism concentrically disposed about the rotor mechanism, and a drafttube assembly operatively connected to the disperser mechanism, whereinthe draft tube assembly provides a path for the raw water into thedisperser mechanism.

In the most preferred embodiment, the skimming means includes anaeration skim tray positioned above the rotor mechanism. The skimmingmeans may also include a secondary oil skimming device positioned withinthe aeration skim tray and configured to direct the oily froth from thevessel. In one preferred embodiment, the secondary oil skimming devicecomprises a cylindrical member with notches at a top end and wherein theoily froth is directed over the notches and into an internal portion ofthe cylindrical member. The rotor mechanism may include a shaftconcentrically disposed within a standing pipe, wherein the standingpipe is attached to the internal portion of the vessel.

In yet another preferred embodiment, an apparatus for treating a rawwater is disclosed. The apparatus includes a vessel having an inlet forthe raw water and an outlet for the skimmed water, a rotor mechanism forcreating a plurality of gas bubbles within the raw water and a dispersermeans, operatively associated with the rotor mechanism, for dispersingthe plurality of gas bubbles from the rotor mechanism. In thisembodiment, a skimming means, positioned about the rotor mechanism, forremoving an oily froth from the top of the raw water is also included.The apparatus further includes an external skim tank that is configuredto deliver a gas to the rotor mechanism and wherein the external skimtank is configured to receive the oily froth and gas from the skimmingmeans. The apparatus further includes a closed loop gas line forcommunicating a gas from the external skim tank to the vessel.

A method of treating a raw water is also disclosed. The method comprisesflowing the raw water into a treatment device. The treatment deviceincludes a vessel containing the raw water, a rotor for creating aplurality of gas bubbles in the raw water, a disperser operativelyassociated with the rotor for dispersing the plurality of gas bubblesfrom the rotor, an internal skim tray for removing an oily froth fromthe top of the raw water within the vessel, an external skim tankconfigured to deliver a gas to the rotor and wherein the external skimtank is configured to receive the oily froth from the internal skimtray, and a closed loop gas line for communicating a gas from theexternal skim tank to the vessel.

The method further comprises channeling the raw water through a drafttube into the rotor, creating a plurality of bubbles within the rawwater, and directing the raw water through the disperser in order todisperse the gas bubbles. The method further includes producing an oilyfroth on a top surface of the raw water, collecting the oily froth inthe internal skim tray, and skimming the oily froth from the skim trayinto a secondary skimming device.

The method further comprises channeling the oily froth through an outputline to the external skim tank and exiting the skimmed water from thevessel. The method may include treating the process stream with carbondioxide within the external skim tank. It should be noted that the stepof treating the oily froth may consist of heating the oily froth withinthe external skim tank.

In one preferred embodiment, the method also includes directing the oilyfroth from the external skim tank to a pump and centrifuge, separatingthe oily froth into an oily component and a water component, and thenchanneling the water component back into the vessel.

Additionally, in one preferred embodiment, the step of creating thebubbles includes communicating a gas from the external skim tank to thevessel via a closed loop gas line. The method may further comprisedirecting the gas in the vessel back into the external skim tank via theoutput line so that the output line is cleaned.

An advantage is that the present disclosure combines components ofseveral novel separation techniques into a single cell apparatus.Another advantage is that the invention provides for a smaller footprintof equipment, which is particularly valuable in remote and/or exoticlocations.

Yet another advantage is the ability to recover oil from primary inducedgas flotation machine rejects and hydrocyclone rejects. Still yetanother advantage is the recovery of oil from produced water streams ona temporary basis while primary water treating equipment is either beingserviced or is too large to be economically operated on the earlyproduction flow rates of the production facilities.

A feature of the present disclosure is a rotor mechanism for creating aplurality of bubbles within the flotation process. Another feature is adisperser for dispersing the bubbles. Yet another feature is theaeration skim tray for skimming the oily froth from the top of theeffluent. Still yet another feature is the secondary oil skimmingdevice, operatively associated with the aeration internal skim tray, fordirecting the oily froth from the vessel.

Yet another feature is the ability to introduce carbon dioxide make-upgas into the closed circulation gas eductor loop for the purpose oflowering the Ph of the produced water which will result in removingwater soluble organic (WSO) content from the produced water. In otherwords, carbon dioxide or other acid gas source is delivered to the rotormechanism either via the external skim tank or directly to theatmospheric space of the vessel for purpose of lowering the pH of theraw water and releasing water soluble organic content from the raw waterand removing the organic content from the raw water by the flotationprocess.

Another feature is the ability to return the effluent water from theexternal skim tank to (1) the inlet of the vessel or (2) with theaddition of subsequent filtration, discharge the water overboard withinacceptable government regulations and industry standards. Put anotherway, the process includes subsequent, additional separation device(s) toclean the skimmed water for overboard or other suitable disposal means.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a partial cross-section end view of the rotor assembly,stand-pipe, and internal skim tray within the vessel of the mostpreferred embodiment.

FIG. 2 is a partial cross-section end view of the disperser, draft tubeand secondary skimmer within the vessel of the most preferredembodiment.

FIG. 3 is a partial cross-section side view of the vessel with theinternal components of the most preferred embodiment.

FIG. 4 is a partial top view of the vessel with internal componentsillustrated in FIG. 3.

FIG. 5 is a schematic illustration of a second preferred embodiment of avessel operatively associated with an external skim tank.

FIG. 6 is a schematic illustration of a third preferred embodiment ofthe vessel operatively associated with an external skim tank and othercomponents.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, a partial cross-section end view of the rotorassembly 2 and stand-pipe 4 within the vessel 6 of the most preferredembodiment will now be described. The rotor assembly 2 is connected to ashaft 8 and wherein the shaft 8 is disposed through the flange cover 10,and wherein the flange cover 10 is affixed to the internal portion ofthe vessel 6. The shaft 8 is spun by a motor means (not shown). As thoseof ordinary skill in the art will appreciate, the rotor assemblyincludes a member capable of rotation within a cylindrical housing sothat during rotation, gas bubbles are produced. Rotor assemblies arecommercially available from Petreco International Inc. under the nameWemco Depurator Rotor Assembly. A gas inlet port 12 for allowing theintroduction of a gas into the vessel 6 via the standpipe 4 and rotorassembly 2 is also shown.

As seen in FIG. 1, the stand-pipe 4 comprises a first outer diameterportion 14 and a second outer diameter portion 16, and wherein theportion 14 is larger than the portion 16. The standpipe 4 is attached atone end to the flange cover 10 and at the second end is attached to theinternal skim tray 18 (also referred to as aeration skim tray 18). Asthose of ordinary skill in the art will recognize, the rotor assembly 2will generate a plurality of bubbles within the raw water which in turnwill cause an oily froth to rise to the top of raw water volume withinthe vessel 6. FIG. 1 also depicts the internal skim tray 18, which formspart of the skimming means. As shown in FIG. 1, internal skim tray 18has a saucier type of shape and is disposed about the secondary skimmer34 (as illustrated in FIG. 2), which surrounds the standpipe 4 and theshaft 8 of the rotary assembly 2. A skim outlet 20 is also shown, andwherein the skimming means is fluidly connected to the skim outlet 20.The internal skim tray 18 will be attached to the sides of the vessel 6.In one preferred embodiment, the bottom of the internal skim tray 18will have open ports 21 a, 21 b for the purpose of limited liquidcommunication between the internal skim tray 18 and the vessel 6. Thisfeature prevents flooding of the internal skim tray 18 by allowingliquids at the bottom of the tray (mostly water) to re-enter theflotation process simultaneously as liquids at the top of the tray(mostly oil) are skimmed into the secondary skimmer 34.

Referring now to FIG. 2, a partial cross-section end view of thedisperser mechanism 24 and draft tube 26 within the vessel 6 of the mostpreferred embodiment is shown. It should be noted that like numbersappearing in the various figures refer to like components. The dispersermechanism 24 is disposed about the rotor assembly 2 (not shown in thisview). The disperser mechanism 24 disperses the plurality of bubblescreated by the rotor assembly 2. The disperser mechanism 24 is acylindrical cage assembly. The disperer mechanism 24 is connected to thedraft tube centralizer 28 which in turn is connected to the draft tube26. The draft tube 26 provides a passage for the raw water that is beingdrawn by the rotation of the rotary assembly 2, as will be more fullyexplained later in the disclosure.

The lower assembly support struts 32 are also shown. The purpose of thelower assembly support struts 32 is to support the secondary skimmer 34,disperser 24, draft tube centrailzer 28, and draft tube 26. FIG. 2 alsodepicts the secondary skimmer 34, wherein the secondary skimmer 34 is arolled piece of metal (i.e. cylindrical) that has several overflow “V”notches (such as notches 36, 38, 40) formed thereon, wherein the skimmer34 is placed within the skim tray 18 (not shown in FIG. 2). An outflowline 42 is in communication with the secondary skimmer 34, and whereinthe outflow line 42 is also in communication with the skim outlet 20 fordischarging the collected oily froth. It should be noted that thesecondary skimmer 34 is placed within the internal skim tray 18, so thatthe oily froth overflows from the internal skim tray 18 and into thesecondary skimmer 34. From the secondary skimmer 34, the oily frothexits via the out flow line 42.

Referring now to FIG. 3, a partial cross-section side view of the vessel6 with the internal components of the most preferred embodiment. Morespecifically. FIG. 3 depicts the rotary assembly 2 connected to theshaft 8. The disperser mechanism 24 is disposed about the rotaryassembly 2 and wherein the draft tube 26 is connected to the dispersermechanism 24, as previously noted. The internal skim tray 18 is disposedabout the secondary skimmer 34.

The arrows A1, A2 represent the circulation path of the raw water thatis being sucked into the draft tube 26 (as noted by arrow A3), which inturn will be drawn into the rotary assembly 2. The raw water will thenbe forced from the rotary assembly 2 thereby creating gas bubbles withinthe raw water, and through the disperser mechanism 24, as noted by flowarrows A4 and A5. From there, the generated gas bubbles will cause theoily froth to rise to the top, and wherein the oily froth will bedirected into the internal skim tray as illustrated by skim tray inlet44 and skim tray inlet 46. The oily froth will collect in the tray 18,and then into the secondary skimmer 34 for removal via the skim outletnozzle 48. FIG. 3 further depicts the raw water inlet 50 for theintroduction of the raw water into the vessel 6, as well as the skimmedwater outlet 52. The skimmed water which exits at the water outlet 52has had the oily froth removed as per the teachings of the presentinvention.

Referring now to FIG. 4, a partial top view of the vessel 6 withinternal components illustrated in FIG. 3 will now be described. The rawwater inlet 50 is shown along with the clean water outlet 52 and skim(oily froth) outlet 20. The top view seen in FIG. 4 also depicts theouter limits of the internal skim tray 18. The internal skim tray 18 issecured to the side walls of the vessel 6. The contour of the flangecover 10 is shown. Also shown is the standpipe portion 16 that extendsto the standpipe portion 14. The rotor assembly 2 is shown disposedwithin the disperser mechanism 24. In the most preferred embodiment, therotor assembly 2 and standpipe 4 are mounted to the flange cover 10 thatbolts to the top of the vessel 6. The disperser mechanism 24, draft tube26 (not seen in this view), and secondary skimmer 34 (not seen in thisview) are all built as a single piece for installation through theflange cover 10. The gas induction nozzle 12 allows the entry of gasfrom the external skim tank (not seen in this view).

FIG. 5 is a schematic illustration of a second preferred embodiment ofthe vessel 6 operatively associated with an external skim tank 60. Theschematic of FIG. 5 depicts the rotary assembly 2 and the dispersermechanism 24 disposed within the vessel 6 as previously described. Theraw water inlet 50 and the skimmed water outlet 52 are shown. The flowarrows A1, A2, and A3 are included, as previously described.

The external skim tank 60 has a gas induction return line 62 that isconnected to the gas inlet port 12. Hence, gas is drafted into the rotorassembly 2 from the external skim tank 60 via gas induction return line62. Additionally, the skim outlet 20 is directed via outlet skim line 64to the external skim tank 60. Besides allowing for a gas circulationpath, the closed loop of gas circulation keeps outlet skim line 64 cleanof the oily froth, which is a feature of the present invention. Make-upgas enters the system through the external skim tank 60 via the make-upgas line 65. Make-up gas is delivered to the system via line 65 from anexternal gas source such as natural blanket gas available on theplatform or an alternate blanket gas source. As per the teachings ofthis disclosure, make-up gas can be carbon dioxide (CO2), wherein theCO2 is added for Ph adjustment to release water soluble organics forremoval via the flotation process to the content of the external skimtank 60.

A skim intermittently means 66 for intermittenly skimming the oily frothwithin the external skim tank 60 is also shown. One embodiment of theskim intermittently means 66 consist of controllers and timers thatremove oil from the surface of the tank and water 67 from the bottom ofthe tank. FIG. 5 depicts a water outlet 67 and associated outlet line 68which directs the water phase component from within the external skimtank 60 to the vessel 6. The outlet line 68 has operatively associatedtherewith the pump means 70 as well as the valve means 72 for directingthe water back to the vessel 6. As an alternative, the water from theexternal skim tank 60 may also be directed to the pump means 74, andwherein for this configuration, the operator may wish to performadditional separation with different types of separation techniques onthe water, or the operator may simply discharge the water in the eventthat the operator feels that the water has been treated adequately.

Referring now to FIG. 6, a schematic illustration of the third preferredembodiment of the vessel 6 operatively associated with an external skimtank 60 and other components will now be described. The liquid componentfrom the external skim tank 60 will be directed to the outlet line 80which in turn is delivered to the centrifugal separator means 82 forseparating the liquid output into a water component and into a oilcomponent. The oil component is delivered to the oil tank 84, andwherein the pump means 86 may be further included in order to pump theoil component to other appropriate holding tanks (not shown).

FIG. 6 also shows where the water component exiting the centrifugalseparator 82 is directed to a water tank 88. A pump means 90 is fluidlyconnected to the water tank 88 so that the water component can be pumpedand delivered to the vessel 6 so that the water component can besubjected to the separation system within the vessel 6, as previouslydescribed. The water component from the pump means 90 is feed into line92, and wherein a valve means 94 is included in line 92 to direct thewater to the vessel 6. The operation of the vessel 6 and external skimtank 60 is the same as previously presented. In this embodiment, it isalso possible to include a divert line 98 and valve 95 to additionalseparation devices 96 such as nutshell filters, sock filters, granularactivated carbon filters 96, diatomaceous earth filters, and otherequivalent separation means. The additional separation device(s) 96 willdischarge clean water through discharge line 97 to overboard or othersuitable disposal means (not shown).

While the present techniques of the invention may be susceptible tovarious modifications and alternative forms, the exemplary embodimentsdiscussed above have been shown by way of example. However, it shouldagain be understood that the invention is not intended to be limited tothe particular embodiments disclosed herein. Indeed, the presenttechniques of the invention are to cover all modifications, equivalents,and alternatives falling within the spirit and scope of the invention asdefined by the following appended claims.

1. An apparatus for treating raw water comprising: a vessel having aninlet for the raw water and an outlet for a skimmed water, said vesselcontaining the raw water; a rotor mechanism for creating a plurality ofgas bubbles within the raw water; a disperser means, operativelyassociated with the rotor mechanism, for dispersing the plurality of gasbubbles from the rotor mechanism within the vessel, and wherein said gasbubbles create an oily froth on the top of the raw water; a skimmingmeans, positioned about the rotor mechanism, for removing the oily frothfrom the top of the raw water.
 2. The apparatus of claim 1 furthercomprising: an external skim tank, wherein said external skim tank isconfigured to deliver a gas to said rotor mechanism and wherein saidexternal skim tank is configured to receive the oily froth from theskimming means.
 3. The apparatus of claim 2 further comprising acentrifugal pump for separating a hydrocarbon component and a watercomponent from the oily froth within said external skim tank, andwherein said water component from said centrifugal pump is directed tosaid vessel.
 4. The apparatus of claim 3 further comprising an internalheat exchange circulation loop 2 operatively associated with saidexternal skim tank so that heat is added to the oily froth.
 5. Theapparatus of claim 1 wherein said disperser means comprises: a dispersermechanism concentrically disposed about the rotor mechanism; a drafttube assembly operatively connected to said disperser mechanism, saiddraft tube assembly providing a path for the raw water into thedisperser mechanism.
 6. The apparatus of claim 5 wherein said skimmingmeans comprises an aeration skim tray positioned above said rotormechanism.
 7. The apparatus of claim 6 wherein said skimming meansfurther comprises a secondary oil skimming device positioned within saidaeration skim tray and configured to direct the oily froth from thevessel.
 8. The apparatus of claim 7 wherein the rotor mechanism includesa shaft concentrically disposed within a standing pipe, said standingpipe being attached to an internal portion of the vessel.
 9. A systemfor treating raw water comprising: a vessel having an inlet for the rawwater and an outlet for a skimmed water; a rotor mechanism for creatinga plurality of gas bubbles within the raw water; a disperser means,operatively associated with the rotor mechanism, for dispersing theplurality of gas bubbles from the rotor mechanism; an aeration skim traypositioned above said rotor mechanism for skimming an oily froth fromthe top of the raw water.
 10. The system of claim 9 further comprising:a secondary oil skimming device positioned within said aeration skimtray, said secondary oil skimming device directing the oily froth fromthe tank.
 11. The system of claim 10 further comprising: an externalskim tank, wherein said external skim tank is configured to deliver agas to said rotor mechanism and wherein said external skim tank isconfigured to receive the oily froth from the secondary oil skimmingdevice.
 12. The system of claim 11 further comprising a centrifugal pumpmeans for separating a hydrocarbon component and a water component fromthe oily froth within said external skim tank, and wherein said watercomponent from said centrifugal pump is directed to said vessel.
 13. Thesystem of claim 10 further comprising an internal heat exchangecirculation loop operatively associated with said external skim tank sothat heat is added to the oily froth within said external skim tank. 14.The system of claim 13 wherein said disperser means comprises: adisperser cage mechanism disposed about said rotor mechanism; a drafttube assembly operatively connected to said disperser mechanism, saiddraft tube assembly providing a path for the raw water into thedisperser cage mechanism.
 15. The system of claim 14 wherein the rotormechanism includes a shaft concentrically disposed within a standingpipe, said standing pipe being attached to the vessel.
 16. An apparatusfor treating a raw water comprising: a vessel having an inlet for theraw water and an outlet for a skimmed water; a rotor mechanism forcreating a plurality of gas bubbles within the raw water; a dispersermeans, operatively associated with the rotor mechanism, for dispersingthe plurality of gas bubbles from the rotor mechanism; a skimming means,positioned about the rotor mechanism, for removing an oily froth fromthe top of the raw water; an external skim tank, wherein said externalskim tank is configured to deliver a gas to said rotor mechanism andwherein said external skim tank is configured to receive the oily frothfrom the skimming means; a closed loop gas line for communicating a gasfrom said external skim tank to said vessel.
 17. The apparatus of claim16 further comprising a centrifugal pump means for separating ahydrocarbon component and a water component from the oily froth withinsaid external skim tank, and wherein said water component from saidcentrifugal pump is directed to said vessel.
 18. The apparatus of claim17 further comprising an internal heat exchange circulation loopoperatively associated with said external skim tank so that heat isadded to the oily froth within said external skim tank.
 19. Theapparatus of claim 18 wherein said disperser means comprises: adisperser cage mechanism disposed about said rotor mechanism; a drafttube assembly operatively connected to said disperser cage mechanism,said draft tube assembly providing a path for the raw water into thedisperser mechanism.
 20. The apparatus of claim 19 wherein said skimmingmeans comprises an aeration skim tray positioned above said rotormechanism; and, a secondary oil skimming device positioned within saidaeration skim tray and wherein said secondary oil skimming devicecomprises a cylindrical member with notches at a top end, and whereinsaid oily froth is directed over said notches and into an internalportion of said cylindrical member.
 21. The apparatus of claim 20wherein the rotor mechanism includes a shaft concentrically disposedwithin a standing pipe, said standing pipe being attached to saidvessel.
 22. A method of treating raw water comprising: flowing the rawwater into a treatment device, said treatment device comprising: avessel containing the raw water; a rotor mechanism for creating aplurality of gas bubbles in the effluent; a disperser operativelyassociated with the rotor mechanism for dispersing the plurality of gasbubbles from the rotor mechanism; an internal skim tray, positionedabout the rotor mechanism, for removing an oily froth from the top ofthe effluent within the vessel; an external skim tank, wherein saidexternal skim tank is configured to deliver a gas to said rotormechanism and wherein said external skim tank is configured to receivethe oily froth from the internal skim tray; channeling the raw waterinto the rotor mechanism; creating a plurality of bubbles within the rawwater; directing the raw water through the disperser; dispersing theplurality of gas bubbles within the raw water; producing an oily frothon a top surface of the raw water; collecting the oily froth in theinternal skim tray; skimming the oily froth from the internal skim trayinto a secondary skimming device; channeling the oily froth from thevessel to the external skim tank in an output line; exiting the skimmedwater from the vessel.
 23. The method of claim 22 further comprising:treating the oily froth within the external skim tank with carbondioxide . . . in order to lower the Ph of the raw water component withinthe vessel and external skim tank for the purpose of releasing watersoluble organic content from the raw water and removing an organiccontent from the raw water by the flotation process.
 24. The method ofclaim 23 further comprising: directing the oily froth from the externalskim tank to a centrifugal pump; separating the oily froth into an oilycomponent and a water component; channeling the water component backinto the vessel.
 25. The method of claim 22 further comprising: treatingthe oily froth by heating the oily froth within the external skim tank.26. The method of claim 22 further comprising: providing a make-up gasto said external skim tank; channeling the make-up gas to the vessel;and, directing the make-up gas back into said external skim tank throughsaid output line.
 27. The method of claim 22 wherein the step ofcreating the bubbles includes communicating a gas from said externalskim tank to said vessel via a closed loop gas line.
 28. The method ofclaim 27 further comprising directing the gas in said vessel back intosaid external skim tank via said output line so that said output line iscleaned.